Alloy



gredient are susceptible I so sistancebutimprovesitsphyslcfl Patented Mar. 1934 ALLOY Robert H. leach,.l'airileld, (ionm, asllgaor to Handy&Harman,NewYork,N.Y.,aeorperation 01- New York -No Drawing. Application June 10, 1552,

Y serial No. 516,500

2 Claims. (01. "-1) This invention relates to silver alloys and is concerned more particularly with a novel silver alloy which maybe used to especial advantage V in the manufacture or table silver and hollow 5 ware and for various other purposes, because it has the property of strongly resisting tarnish and discoloration. V

As is well known. silver alloys of ordinary composition and containing copper as the base into tarnish. Such discoloration of the metal is brought about by which is present in various foods such as eggs, and it is also present to some extent in the atll mosphere in the form oi gaseous compounds. Sulphur in both forms causes tarnishing at a rate which depends on the length of contact or 1 exposure of the metal, the concentration oi the sulphur in the food or air, and the form in which II the sulphur is present. In any event, the necessity oi frequent cleaning and polishing or silver articles to keep them in bright condition has led to numerous attempts in the past to produce 'silver alloys which are of goodappearance, have 55 the desired working characteristics, and have a -betterresistancetotarnishthanordinarysllvercopper alloys, but up to the present, the proposed alloys with which I am-iamiliar, have not proven entirely satisiac -'1'he problem of producing a silver alloy which is resistant to tarnish-is a diiilcult one because investigation hasshown that binary alloys oiier.

little promise and the number of ternary and quaternary alloys is very large.- When it is understood that small variations in the ingredients in these alloys have an important eflect, on the resistance totarnish and the amounts or the alloying ingredients used is highly critical with respect to tarnish resistance, the magnitude and 40 difllculty of the problem will be appreciated.

' As a result of my investigations in this ileld, I have found that a silver alloy which has excellent resistance to tarnish produced by various agentsmaybemade byusingtinandmagnesium as as alloying metals, provided these ingredients are confined within relatively narrow limits; In

-fineness has the following approximate agent but its eiiect is less amount which increases the tarnish resistance may have little hardening action. 1 Asilver alloy otsterlingflnenesmmadeinav cordance with the invention, contains not less than about 92.5% silver. tin rangins from about so 4% to about 6.5%. magnesium rangins from about 0.5% to about 3%, and one or both of the metals chromium and antimony as hardening elements with these metals present. in a total amount ranging from about 0.25% to not sub- 05 .stantially in excess or 1.5%. numerous agents, the most active being sulphur A typical example or the new alloy of sterling analysis;

Per cent silver 9 Tim 1 Magne um 1- Chromium .lhenew alloyishkhlyresistanttotarnishu and corrosion and it may be given the physical characteristics by the addition or thehardening elements in proper amounts. 1 preq ierto use chromium tor purpose and ordinarily it is not necesary employ more than 0.5% of this metal. The use of chromium in such an amount makes the alloy sufliciently hard for ordinary purposes and the hardness may be increased by increasing the amount of chromium. Antimony also acts as a hardening as pronounced than chromium. Both chromium and antimony in the amounts specified increase the resistance of the alloy to tarnish and are substantially equivalent ror the purpose mentioned.

what I claim:

magnesium ranging from about 0.5% to about 3%, and chromium ranging from about 0.25% to as;

.about 1.5%.

ROBERT a, 1m

addition to the tinand magnesium, the new alloyalsocontainsasmallamoimtoiaiourth ingredient which not onlyadds toitstarnish reprope es. The fourth ingredientmaybeoneorbothorthe metals,chromiumandantlmony,andlshallrefei-tothisiiigretlientas'o.liarn ienei",although thehardening eilect depends considerably on u the amount ot theingredient present and 'an ios 

